Tell me what to do

1. Tell me what to do Using sets of instructions… Module 1- Getting Started

2. Consider these 3 situations…. • Baking a Cake • Giving Directions • Buying items in a shop

3. What do all 3 have in common? • They are all sets of instructions. • They all solve a problem. These are called Algorithms.

4. A good algorithm • Leads to completion. • Is accurate and unambiguous. • Has the appropriate level of detail. • Has well ordered instructions. • Covers all possible outcomes with practical solutions.

5. Human vs Computer Algorithms • With human algorithms we can rely on • Intuition • Initiative • Prior knowledge • Independent decision-making • Learning from experience • Computers do not have these things and therefore we must take this into account when we write the algorithm for a computer program.

6. Write an algorithm…Solve the farmer’s problem • A farmer has to take three items, a dog, a goat and a cabbage, across a river. He has a boat but it can only take two objects at once, in other words, the farmer and one other item. • Write an algorithm to tell the farmer how to get the three items across the river. • Note: If the dog and the goat are left together the dog will eat the goat. If the goat and the cabbage are left together the goat will eat the cabbage.

7. The Farmer’s Solution… 1.    Begin on side A 2.    Take goat across to side B 3.    Return with empty boat to side A 4.    Take dog across river to side B 5.    Return with goat to side A 6.    Take cabbage to side B 7.    Return with empty boat to side A 8.    Take goat to side B 9.    END

8. Top up your mobile phone credit! How?

9. Possible solution 1. Buy a top up voucher in a shop or at a vending machine. 2. Dial 1741 on your phone. 3. Listen to the instructions. 4. Enter the code on the voucher and press the # key on your phone. 5. Listen for your new balance to make sure it’s correct. 6. Hang up.